406 
POPULAE SCIENCE EEVIEW. 
result obtained from the observations on mountain sides^ on 
the decline of temperature with increase of elevation — viz., 
the lowering of temperature of the air 1° for every increase of 
elevation of 300 feet. 
The next in order of importance was the law of the distri- 
bution of the water in the air, in the invisible shape of vapom^, 
near the earth, near clouds (but below them), in different kinds 
of clouds, and at high elevations above the clouds. These 
determinations to be made by the use of different instruments 
— viz., by Daniehs hygrometer, Regnault^s condensing hygro- 
meters, by dry- and wet-bulb thermometers, as ordinarily used, 
as well as when under the influence of an aspirator, so that 
considerable volumes of air could be made to pass over both 
their bulbs at pleasure. 
To compare the results thus found together : firstly, to 
determine whether Daniehs or Regnault^s hygrometer were 
the better instrument ; secondly, to compare the results as 
found by the use of the dry- and wet-bulb thermometers, as in 
common use, with those under the action of the aspirator; 
thirdly, to determine what confidence could be placed on the 
use of the dry- and wet-bulb thermometer at high elevations, but 
particularly up to those heights where man may be resident, or 
where troops may be located, in the highlands and plains in India. 
To determine the effects which the sun produces upon deli- 
cate thermometers, exposed to its full influence, at different 
heights, in excess above the readings of equally delicate ther- 
mometers protected from the direct beams from the sun ; and 
also the effect the sun exercises on the readings of HerscheTs 
actinometer, at different heights, when fully exposed to his rays 
at different elevations, in comparison with the increase of 
readings in the same interval of time when on the ground. 
To determine whether the solar spectrum, when viewed 
from the earth, and when examined far above the earth, ex- 
hibited any difference; whether there were more or less 
black lines crossing it ; whether these lines were better defined 
or not ; and whether, towards sunset, there was any increase 
in the number of these lines. 
To compare the readings of mercurial barometers and 
aneroid barometers together. 
To determine the electric state of the air. 
To determine the oxygenic conditions of the atmosphere by 
means of ozone papers. 
To determine the intensity of magnetism. 
To collect air at different elevations. 
To note the kinds of cloud ; their heights at their lower and 
upper surfaces ; their density, &c. 
To collect information about the currents of the atmosphere. 
